Patterns of Sensitization and Cross-Reactivity in Hair Dye Allergy: An 18-Year Tertiary-Center Experience from Greece.

The study conducted over 18 years at the Andreas Sygros Hospital in Athens, Greece, analyzed patch-test results from 666 patients with suspected hair dye-related allergic contact dermatitis (ACD). It found that 82.4% of patients reacted to at least one allergen, with para-phenylenediamine (PPD) being the most common (47.9%), followed by toluene-2,5-diamine (TDA) and nickel. Significant co-sensitization was observed between PPD and related compounds, such as aminophenols and benzocaine. Hairdressers, who were generally younger, predominantly experienced hand dermatitis. The study highlights the need for extended patch testing for accurate diagnosis and suggests that safer hair dye formulations and preventive strategies are necessary due to occupational exposure and multi-allergen sensitization.